Where we look betrays what we’re thinking. For instance, given a choice between two snacks, people spend longer looking at the alternative that they ultimately choose. A new study digs deeper into this process and asks: is gaze direction also related to moral choices, and does it actually influence those choices?

Twenty students donned an eye tracker and made a series of moral judgments. On each trial, the students heard a statement over headphones (e.g. “murder is sometimes justifiable”) and then two options appeared on either side of a computer screen (e.g. “sometimes justifiable” on the left side, “never justifiable” on the right) – the students’ task was simply to indicate by button press which of these options they believed. They were told they would be prompted to make this decision after a random amount of time had passed.

Daniel Richardson and his colleagues found that if they prompted the students to make their decision after they had looked at one of the options for at least 750ms (and the other for at least 250ms), then it was more likely than not the students would choose the option they’d spent more time looking at (59.6 per cent of the time they chose this option). This replicates previous research showing we tend to look more at our favoured option, even when making weighty moral choices. Yet, asked afterwards, the students were unaware there had been any link between the timing of the decision prompt and their eye gaze.

In a second experiment, the researchers wanted to see if gaze can actually influence people’s moral choices. The researchers selected on each trial which option they wanted the students to choose and tried to influence them to make this choice. To do this, they waited until each student had spent at least 750ms looking at the target option (and at least 250ms looking at the non-target) and only then prompted them to make their decision. Following this procedure, the students more often than not chose the option that the researchers wanted them to choose (58.2 per cent of the time the manipulation worked). Further analysis showed that participants were more likely to make a choice if they’d looked at it more, and if it was the option they were looking at when they made their decision.

“This means,” the researchers said, “that knowing when participants are looking at alternatives gives sufficient information to change the course of their decisions.”

When students chose the target options, they tended to be quicker in indicating their choice, and more confident in their decision. This reinforces the idea that eye gaze is somehow connected to, and reflective of, unfolding decision-making processes, such that it’s easier to make a decision when looking at the option that you plump for. By tapping into this process and manipulating the timing of a person’s decisions, these new findings suggest it’s possible to influence people’s judgments, even for weighty moral choices.

“Although moral decisions can be debated at leisure after the fact, they are also made in the moment,” the researchers said. “We find that the precise timing of those moments can be a powerful influence on the choices we make.”